Electric air heater



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1949. J. s. WRIGHT 2,477,778

ELECTRIC AIR HEATER Filed March 8, 1948 2 Sheets-Sheet 2 INVENTOR. Jaw/v 6. WR/GA I' BY wwwwww ATTOR/Vf YS Patented Aug. 2, 1949 1 UNITED STATES PATENT OFFICE a i .2,477,'778

ELECTRIC AIR HEATER John S. Wright, Adrian, Mich.

Application March 8, 1948, Serial No. 13,542

The invention relates to electrical air heaters of that type in which a medium of steam or water vapor is interposed between the electrical heating units and the radiatin surfaces which come in direct contact with the air. This pre- Vents the burning of any organic material which may be carried in suspension and thus avoids pollution of the heated air. With apparatus of this character it is desirable to seal the chamber in which the Water vapor is generated so that the pressure may be less than atmosphere with the correspondin lowering of the temperature of the radiating surfaces. Also this conserves the water and avoids the necessity of frequently renewing the same. However, the pressure of the steam or water vapor depends on two factors, first, the rate of heat generation; and, second, the rate of heat dissipation. If, therefore, the rate of dissipation should be less than that of generation the pressure will mount in the vapor chamber and may burst the seal.

It is the object of the instant invention to obtain a construction of an electrical air heater of the type above mentioned in which rise in pressure of the vapor to an objectionable point is effectually prevented. To this end the invention consists in a construction where the rate of heat dissipation relative to that of heat generation is so controlled that the pressure will not rise above that of atmosphere.

The invention further consists in the specific means by which such result is accomplished as more fully hereinafter set forth.

In the drawings:

Fig. l is a front elevation of my improved electrical air heater;

Fig. 2 is a cross-section therethrough;

Fig. 3 is a longitudinal section through the heating unit.

The electrical heating unit together with the steam generating chamber and radiating fins may be similar in construction to that shown in my former Patent 2,225,850, issued December 24, 1940. Also this unit is placed within a casing through which air passes in an upward direction to be heated during such passage. In this former patent it was assumed that control was dependent on only two factors viz., first, the rate of heat generation; and, second, the area of the heat radiating fins or surface area in contact with the air. These two factors are not, however, sufficient to effectively control the apparatus for there is also the factor of the temperature of the air which comes in contact with the radiating surface; and, second, and more im- 3 Claims. (Cl. 219-38) 2 portant, the velocity of theair current which traverses these surfaces. Consequently, failure to consider such factors may result in rise of pressure within the sealed chamber and the breaking of the seal. With my improved .construction more perfect regulation is accom plished by first determinin a maximum temperature for the air which comes in contact with the radiatin surface; and, second, designin the casing or passage through which the air flows so as to obtain a predetermined velocity of movement of the air. Thus with a generating unit of predetermined capacity the rate of air flow may be regulated by increasing or decreasing the height of the chamber through which the air travels. If the height is increased there will be a longer column of heated air with a greater difierential between the weight of the same and that of a column of external air of the same height. This will increase the velocity of travel. On the other hand, a decrease in heat of the chamber will correspondingly decrease the rate of flow with the result that the rate of heat dissipation is reduced.

My improved construction is, therefore, onein which the height of the casing is selected with respect to the generating capacity of the heating unit so that the pressure within the vapor chamber cannot exceed a predetermined amount. As specifically shown the heating unit has two cylindrical casings A and A which are preferably relatively positioned so as to not be in vertical alignment. This provides a freer flow of air in an upward direction as the upper cylinder is not directly in the path of the air from the lower cylinder. Each of the cylinders A and A has arranged therein an inner casing, and these casings B and B are concentric with and spaced from the outer casings to form a fluid holding chamber therebetween. Electrical heating units 0 and C" are placed within the inner casings B and B and are insulated therefrom by refractory insulator bodies D and D. The two casings A and A are connected to each other at one end by an obliquely extending conduit E. Both of these casings contain water, but the upper casing has a vapor space in a portion thereof which is sealed preferably when the temperature of the water is at boiling point so that this space is filled with steam. Thus at any temperature less than the normal boiling point of water, the vapor pressure within the casing will be less than atmosphere. At their opposite ends the casings A and A have a connection F through which liquid from the casing A is passed upward into a spray tube G 3 in the casing A above the inner casing B. There is also a baflie H in the casing A for restricting the flow of liquid therethrough, so that generation of steam beyond the baffle will produce a geyser effect lifting liquid through the tube F and discharging it through the jet tube G. As the jet tube G is in the steam space above the water level in the casing A, it will direct water against the portion of the casing B which is above the liquid and 'therefore, more highly heated. Consequently, the spray contacting this surface will be flashed into steam, and the steam will be condensed against the outer casing A imparting its latent heat thereto. The casings ,A and A have secured thereto a series of fins I .of-rectangular form which constitute an extension Qf the heat conducting surface. This completes the generating unit which is placed'within the outer casing J, preferably formed of sheet metal. The casing J is supported on legs J to raise it from thefioorandhas an .openbottomfor admission of air. At the .upper end and at the front of the casing is a ,grille K through which the heated can pass outward to commingle with the air .in .the room. .A curved shield .L direct th ascending air current towards this grille.

The casing ,J forms in efilect .a chimney and the velocity of the air current ascending through this chimn y is dependent .upon its height and capacity. The dimensions .of the casing J are therefore calculated .to produce a predetermined velocity of air flow therethrough such that .Iiea't will be transferredfrom thefins lto the aincurrent as rapidly asit is being generated by th electrical heaters. In other words, .theheat generating capacity of electrical heaters, the heat ,dissipating capacity of the radiator and the velocity of the air current ,are proportioned to .each other. Assuminga maximum temperature ,for the air entering the heater, these {parts are so proportioned that the vapor pressure within the casing A will not exceed .a predetermined amount such, for instance, as that of the external atmosphere.

What .I claim as my invention-is:

.1. The combination with a heat generating and dissipating unit, comprisinganencased electrical heater, a radiator, surrounding and spaced therefrom forming ,a sealed chamber therebetween, andiavaporizableiliquid in:said-chamberiior ning rauheat transmittmg medium betweenisaidheater sandrradiator of a chimneys easing-in which-said unit is, placed to cause :an upward current of zair contact ,with-.-said radiator, -.-said. casin fleein .eso proportioned 1 in height ,and capacity irelative 4 to the heat generating capacity of said unit as to transfer the heat of the latter to the air at a rate which limits the temperature retained within said sealed chamber to that preventing rise of vapor pressure in said chamber above a predetermined limit.

2. The combination with a heat generating and dissipating unit, comprising an encased electrical heater, a radiator surrounding and spaced therefrom forming a sealed chamber therebetween, and a vaporizable liquid partially said chamber, the vapor pressure on said liquid being ,less than that .of atmosphere when the heater is ,not in operation, said liquid and vapor forming a heat transmitting medium between the heater and radiator; of a chimney casing in which said unit is placed to cause an upward current of air'in contact with said radiator, said casing being so proportioned in height and capacity relative to the heat generating capacity of said unit as to transfer the heat of the latter to theair at a rate which limits the temperature retainedwithin said sealed chamber to that preventing rise of yapor pressure in said chamber above the pressure of atmosphere.

:3. The combination with aheat generating and dissipating unit, comprising an encased electrical heater, a radiator surroundingand spacedtherefrom forming a sealed chamber therebetween, and ,a vaporizable liquid partially filling said chamber, the vapor pressure on said liquid being less than that of atmosphere when the heater is not in operation, said liquid and vapor forming a heat transmitting medium between the heater and radiator; of a chimney casing in which said unit is placed to cause an upward current of air in contact with said radiator, said casing being so proportioned .in height and capacity relative to the :heat generating capacity .of said unit as to maintain a velocity of air passing the radiator limiting the heating thereof to a relatively low temperature differential between said airand-that of the external atmosphere thereby facilitating th pmm nelin of th sa JOHN S WRIGHT.

REFERENCES CITED The following referenlces are of record the ;,flle of this patent:

UNITED STATES PATENTS Number Name. ,Date

1,983,437 Carr V =Dec. ,4, .1934 2,041,573 Shapard ,,May 19, 1936 2,225,850 Wright g Dec. 24,1940 

